Email is still where most breaches start. These are the platforms that actually catch business email compromise, not just the spam your gateway already blocks.
LC
Louis CorneloupFounder, Dupple · 600,000+ readers · Updated Jul 2026
Independently researched. No pay-for-placement.5 tools compared
TL;DR
The best email security tools in 2026 are Abnormal Security for stopping business email compromise on cloud mailboxes, Proofpoint for large enterprises that want the deepest threat intelligence, Microsoft Defender for Office 365 for the best value if you already pay for E5, Mimecast for teams that also need archiving and continuity, and Barracuda for smaller shops and MSPs. Your deployment model, gateway or API, matters as much as the detection engine.
More than nine in ten attacks arrive by email, and the ones that hurt are rarely malware. They are a convincing message from a spoofed CFO asking for a wire transfer, or a hijacked vendor account sending a fake invoice. Legacy filters catch spam and known-bad attachments and miss exactly this. We looked at how each platform detects impersonation and account takeover, how it deploys, and what it really costs once you count the modules a security team needs. Here are the five worth a bake-off.
Top Picks
Based on features, real-world fit, and value for money.
An email security tool inspects inbound, outbound, and often internal mail to block phishing, malware, business email compromise, and data leaks before they reach a user or leave your organization. Older products are secure email gateways that reroute your MX record and scan mail in transit. Newer ones connect through the Microsoft 365 or Google Workspace API, read signals the gateway never sees, and pull malicious messages back out of the inbox after delivery.
Why it matters
Attackers moved past malware because identity is easier. A payment-fraud email carries no attachment and no link for a scanner to flag, so it sails through a signature-based filter and lands in front of a busy employee. The average wire-fraud loss runs into six figures, and one compromised internal account can phish your whole company from a trusted address. Email is the single most attacked channel, which makes the layer that watches it one of the highest-return controls most teams own.
Key features to look for
Phishing and BEC detectionEssential
Behavioral analysis that flags impersonation, payment fraud, and social-engineering messages that carry no malware and slip past signature-based filters.
Malware and malicious URL defenseEssential
Attachment sandboxing plus link rewriting and time-of-click scanning, so a URL that turns malicious after delivery is still caught.
Account takeover detectionEssential
Spots a compromised internal mailbox sending lateral phishing from a trusted address, which external-only filters never see.
Deployment model
Gateway products reroute your MX record; API-based products connect to Microsoft 365 or Google Workspace with no mail-flow change and faster rollout.
Automated remediation
One-click or automatic pull of malicious mail already delivered to inboxes, plus an abuse mailbox and a user-report button that feeds triage.
Data loss prevention and encryption
Outbound controls that stop sensitive data leaving by email and enforce encryption on regulated content.
Mistakes to avoid
×Assuming your Microsoft 365 or Google filter is enough. Native filtering catches spam and known malware but misses the payment-fraud and impersonation emails that cause the biggest losses.
×Buying on malware-catch rates alone. The threats that matter now carry no payload, so test each tool against real business email compromise samples, not signature detection.
×Ignoring outbound and internal mail. A hijacked internal account phishing your staff from a trusted address is invisible to a tool that only inspects inbound traffic.
Expert tips
→Run a two-to-four week evaluation on live mail before you switch. API-based tools sit alongside your existing filter and show exactly what they would have caught.
→Turn on the user-report button and route it into automated remediation, so a single report can pull the same malicious message from every inbox.
→Layer, do not just replace. Microsoft or Google handles bulk spam cheaply, and a dedicated tool adds the BEC and account-takeover detection they lack.
The bottom line
If your mailboxes live in Microsoft 365 or Google Workspace and business email compromise is your real worry, start with Abnormal Security, its behavioral model catches what gateways miss and deploys in minutes. Large enterprises that want the deepest intelligence and tightest compliance controls should look at Proofpoint. If you already pay for E5, Microsoft Defender for Office 365 is the value pick, and Mimecast earns its place when you also need archiving and continuity. Smaller teams and MSPs are well served by Barracuda. Test any of them against live mail before you commit.
Frequently asked questions
What is the difference between a secure email gateway and an API-based tool?
A gateway reroutes your MX record and scans mail before it reaches the mailbox, which means an MX change and more setup. An API tool connects directly to Microsoft 365 or Google Workspace, deploys without touching mail flow, and can see internal messages and pull malicious mail back after delivery.
Do I still need email security if I use Microsoft 365?
Yes for most teams. Microsoft's built-in filtering handles spam and known malware well, but dedicated tools are stronger against business email compromise, impersonation, and account takeover, which are the attacks that cause the largest financial losses.
What is business email compromise?
Business email compromise is a fraud where an attacker impersonates an executive, vendor, or colleague to trick someone into wiring money or sharing data. These emails usually carry no malware or links, so they defeat signature-based filters and need behavioral detection to catch.
Can one tool replace my whole email stack?
Often, but many teams layer. Microsoft or Google handles bulk spam cheaply, and a dedicated platform adds the advanced phishing, BEC, and remediation those native filters lack. Test on live traffic to see what each one actually catches for you.
